Thursday, 11 September 2014

ROG Britannia

Here's a challenge for those who want theirs in  1590B. Should fit, but it'll be a challenge.

From ROG:
The English Channel was our first attempt to adapt the Vox AC-30 Top Boost amplifier for use as a guitar pedal. Released in 2004, the English Channel was a straightforward JFET implementation that was heavily based on the amp's schematic using the so-called "FET by numbers" approach. While this approach did certainly capture the amp character to certain degree, the overall sound of the resulting circuit was not as refined as its valve counterpart.

Through the years since the English Channel was released, we've been polishing the manner in which the different valve stages used in guitar amps are adapted to JFET-based circuits. This involves taking several aspects into account, such as the effective frequency response of the stage after considering parasitic capacitances, input and output impedances, gain and dynamic range, and clipping characteristics. Furthermore, in some cases we have taken the artistic license to replace certain portions the circuit with something that provides the intended function without necessarily looking like the original circuit.

Now we present Britannia, a fully redesigned adaptation of the AC-30 for use as a guitar pedal which has been optimized for playing into a clean solid-state amp. We hope that you will find this project a nice approach to the sound that was made famous by many artists, including The Beatles, Tom Petty, The Edge, and Brian May, to name a few, without having to invest in or carry around the real thing.

Here is the usual circuit walkthrough for those interested in the savory details: First, Q1 is our standard high impedance input stage, very "booster friendly" thanks to the two red LEDs at the Gate. Next, you will readily recognize a scaled version of the Gain control section, which together with Q2 form a treble booster. You will also notice that all JFET stages but Q2 are prevented from clipping hard by virtue of the back-to-back diodes present at each Gate. This helps retaining the sweetness and dynamics of the sound. However the original amp has some degree of grittiness in it when pushed hard, and this is achieved specifically by Q2, which is a high gain stage borrowed from the Omega booster. Apart from its higher gain, this stage is generous in 2nd order harmonics. Then comes Q3 as a voltage follower driving a slightly modified version of the original tonestack. Some additional gain is provided by Q4, then a cousin of the original Cut control, which in our case was wired backwards with respect to the original, and therefore labeled Brilliance. Next, the op-amp U1a provides the final touch of soft overdrive, followed by U1b that implements the ultimate toneshaping: a 200 Hz resonance characteristic of a 2x12" cabinet and some high frequency rounding.

Jon Patton's official demo:




Working voltages as posted by ξεναγός νεκρόπολης:

q1
d 6,05
s 0,89
g 0

q2
d 5,06
s 2,42
g 0

q3
c 8,55
b 5,62
e 5,43

q4
d 5,42
s 1,10
g 0


1 4,21
2 4,21
3 3,8
4 0
5 2,09
6 4,21
7 4,21
8 8,43

34 comments:

  1. This is simply a great pedal. The video, I think, doesn't really do it justice, although I really like Jon Patton. Truly, a fascinating take on the Vox AC30 sound.

    check out my build notes using the PCB I bought from 1776 Effects.
    There is a clip on the bottom of the page there.
    http://fuzzquest.blogspot.co.il/2014/06/britannia-new-british-channel-by.html

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    Replies
    1. Your demo is really cool, Doron. the art on the enclosure is very good too.

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    2. Thanks man, I hope my blog can help people decide on which pedals they should build.
      Fuzz lovers have a very hard life because they are never satisfied with the pedals they have and they literally build dozens of pedals to reach the arsenal of sound they are after.

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    3. By the way, what are your "top five" OD pedals so far?

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    4. Talking strictly OD with no Fuzz pedals around I would say that my top 5 are (Not necessarily in that order):
      Catalinbread RAH (King WATT on my page).
      Wampler Plexi-Drive (close but better refined than the the ROG Thor).
      ROG Azabache (Tweed Palette on my page).
      ROG Britannia (Better sounding than the English Channel).
      ROG Supreaux Deux (Page 1 on my page).

      These 5 mark my coverage of the great 5 amps of the 60's: Hi-Watt, Marshall, Fender, Vox and the Supro as a bonus. These amp-like pedals always sound more natural to me than the OD pedals which are less delicate and more distortion like.

      The other great sounding OD which did not make this list but are still really really great are:

      ROG Ginger (really great for guitars too, not just bass).
      Landgraff LDO (Scream-a-delic on my page - classic TS with an edge).
      Pro-co RAT (The Bat on my page - again a classic distortion).
      Sam Ash Astro-Tone (Although it's a fuzz, it's got some really nice OD crunch).
      ROG Umble (Tumble Drive on my page - hard OD and more distortion sounding).

      I Guess the more pedals I build the more confused I get but there are about 20 more pedals I wanna build and add to the list:
      BJFE Honey Bee, Wampler Tweed, Crimson Drive, DBA Interstellar Overdrive, AM King of Tone, Voodoo Lab Sparkle Drive, Zen Drive and a Klon Centaur.
      How about that for my next 8 OD builds? Man, this stuff never ends.

      Good Luck !

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    5. So true! I really dig these "amp sim" analog circuits. I have built the RAH, Plexi and the Supreaux (the first version, not the Deux), too. The Sweet Honey, Zen Drive were the 1st and 3rd pedals I've built, respectively. These are all great OD's. I'm not much of a fan of TS type OD's, though - I just sold a Sparkle Drive today to a friend after a gig, can you believe that? For something tone-wise "related" but, IMO, "better" than average TS-pedals I'd go with the Zen.

      ROG Prof. Tweed and Thor are the next ones in my list (the first one just needs wiring and the Thor has the stripboard already prepared - I'm using Miro's layout for both). Next ones will be a Madbean delay, ROG Tri-Vibe and Azabache.

      I have also built quite a few non-commercial designs just out of curiosity that sound awesome.

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    6. Great man. So how would you rank your favorite 5?
      btw. ROG Tri-Vibe is a fantastic sounding pedal.

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    7. Taking in consideration both sound and usefulness (I play in a classic rock/power pop band):

      1- Sweet Honey/Supreaux. the Supreaux probably wins by a nose (or two) - it has a more useful tone control and a little more gain at higher settings. Both are just as dynamic and overall, sound very similar (I have published a vero layout I made for it in the Forum here and at TDPRI). Love them with my Tele. Both work great for low and medium gain, boosters, always-on pedals, you name it and do all those really well.
      2- Timmy (Love this one with my Strat, not so much with a Tele). Great "can't go wrong with" pedal that would please most players, maybe even more than the SHOD/Supreaux. Love the EQ section and to use it as a boost after another OD.
      3- RAH. Really shines with humbuckers. Lots of punch and definition but not as dynamic as other pedals of the same vibe (read "British OD" type of thing). Really good with single coils too. Mine is modified for extra gain. Can get some Vox-y tones too.
      4- Plexi Drive - easier to get dialed in than the RAH. I haven't used it live yet but sounds very promising. It kind has a clinical, very pristine sound that may not be as natural as the Eighteen, per example, but the gain/tone ranges are excellent.
      5- ROG Eighteen - More limited regarding tonal options, meaning that there isn't a lot of gain and the tone control is less effective than the Plexi's or RAH's - but what a tone! None of my other British style pedals sound so rich in lower gain settings as this one. Fattens up tone a bit too. I removed the 200pf cap because it made the pedal sound very bright even with the tone control quite low. I'm also going to lower the master volume pot to a 25K one since it's VERY loud in the first quarter of the dial. Has a very distinct bark when you hit the strings hard that is really natural sounding. Loses for the Plexi because it doesn't have much gain range (modified mine with a 1M pot but it's still not much) and tone settings.

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  2. Want to build this one some day - everything ROG that comes out is always of my interest. Jon's demos are nice, I like to hear what he says to say about each build/circuit in particular - but his fingerstyle approach for everything is not for me.

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  3. I too have the 1776 PCB and plan to build this soon, as I now have the right angle PCB mount pots that I need. The vero layout looks very nice - good job Mirosol.

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  4. Build the 1776 PCB. Nice drive and awesome PCB!

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  5. a day before miro posted the vero, I etched a PCB for it from the ROG site, and tested it. it sounds great. now I just need to box it up.

    here's a pic of the board:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Britannia/001-BritanniaPCB-01.jpg

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  6. Thanks, I've been putting off building one for myself, I'll use this new layout for mine!

    I built one a while back for a guy using the layout by albru80 posted in the forums here:

    http://guitar-fx-layouts.42897.x6.nabble.com/ROG-Britannia-td8496.html;cid=1410418754253-530

    I had added a bypass-able Dan Armstrong Red Ranger at the input (IMO the treble boost and full range boost sounded great with this pedal, the bass boost not so much). And with the help of Jon Patton, I flipped the brillance control to a top-cut control as the guy wanted a Wampler Thirty Something look to the pedal. Sounded great and albru80's layout worked perfectly, but there were some resistors standing up a bit.

    The Jangler a.k.a ROG Brittania & Red Ranger: https://lh3.googleusercontent.com/-nLdMSJPLtfE/U9Rsl24JdaI/AAAAAAAAABU/DV93rm59Gcw/w395-h510-no/Jangler.png




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  7. mine's done. yay!

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Britannia/Britannia-01.jpg

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Britannia/Britannia-02.jpg

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    Replies
    1. As always, great design, well thought and quality looking.

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  8. tag it miro!
    verified

    or at still everything is working ok, except one thing...
    i only have 2n5458 jfet...no j201 at all...i could only find those j310 and so i started building this....but they suck in this one...it was like a fart, so i've put and a third 2n5458 and the only thing now is that it has the half gain of the original...which i suppose comes from the wrong transistors as sound became really good by the time i changed it.
    all pots are working, and one more thing.
    the trimmer for q2 couldn't go not even close to 5v. so i took it out and put a 300k so i can bias this thing.
    i have almost no experience with jfet builds just cause i can't find any here...i know time for a big order is near...at least those stupid j201

    ahh! i almost forgot it. the volume at max is just above unity. so maybe a 20k would be better or not?
    thanks for the great work
    hope i'll get soon those j201 to make a new review

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    Replies
    1. Damn! Thanks man! I'll tag it right away..

      As a hint, check aliexpress for J201s. Decent price for a hundred pieces...
      +m

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  9. nice mate. i found them. really cheap...thanks...
    25$ for 100 pieces i think is a great deal...
    but i'll try to find a supplier who will have the isd1420 ic too and some other small things, to avoid double fees...last time i bought from china(alibaba), all the staff was about to 140 euros, and shipping and fees were 210...
    but still very cheap if you consider what i got...
    so...tomorrow i'll go shopping...

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  10. Hi all..

    I'm new to the site (which is fantastic BTW) and have been doing a little (a lot of) reading various layouts. I haven't ever built a layout from scratch, but I'm handy with an iron from doing my own guitar electronics for years.

    I would like to start the habit and for my first purchase I want to secure a whole bunch of J201's as these seem to be the primary component in many builds that I favour and are fast disappearing (at least in usable quantities).

    I noticed above that you recommend Aliexpress. I had a look and there seems to be a whole bunch of 100pc lots at various prices in the late $0.20 price range.

    Can you recommend a particular link on there or should I just shoot for the cheapest?

    Some 2n5457's are also on the list; any recommendations there also?

    Thanks in advance..

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  11. miro!
    there is an update!
    i made it work as it should with out changing jfets!
    i found just one mistake which changed everything.
    i was thinking that just a different jfet shouldn't make such a big difference in the hole gain thing.
    it was like just a boost and nothing like overdrive.
    so i took the schematic and i found that
    the 1k resistor from pin 7 is wrong
    it should start from pin 6 then 4.7uf and ground
    now it has as much gain as i ever needed for an o.d.!
    it's absolutely fantastic.
    yesterday i could hear the "like a tube" thing that i've read somewhere...
    but now it's all right here...the best overdrive till now for me.
    so just with 3x2n5458 it can do the job but i'll put for sure those j201 when i 'll get them!

    and one more thing.
    the schematic on the 9v part, gives one 220uf cap. the one from pin 8 lets say. the other 220uf is a 10uf. i 've changed that to.
    great pedal again.
    thanks a lot man!

    tomorrow i'll post the working voltages

    ReplyDelete
    Replies
    1. Thanks for heads up! These things happen :)

      Both fixed on the current version.
      +m

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  12. Hi all!
    Can i use this layout in conjunction with a cab sim (the cab from AMT S1 Legend for example) and have an "amp-in-a-box" kind of pedal to go directly to a DI and then to a PA, computer or anything?
    Thanks!

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    Replies
    1. Sure you can. Actually, the ROG circuits sound really good with amp simulators and this is why I like building them so much. They sound great with real amps too, but cab simulators are really just equalized and phased tone shapers.

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    2. Thanks!
      I'll try to build that couple with a headphone option.

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  13. I asked this question in the Forum and the key is going into a DI box prior to going to your PA or computer. You probably don't need a cab sim pedal (e.g. ROG Condor), but I think that having one would provide more flexibility. It would be nice to gig with an all pedal rig (e.g. boost + overdrive + Britannia + cab sim + delay/reverb --> DI Box --> PA) - no heavy amp to haul around! :)

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  14. working voltages in my build which is as described above

    q1
    d 6,05
    s 0,89
    g 0

    q2
    d 5,06
    s 2,42
    g 0

    q3
    c 8,55
    b 5,62
    e 5,43

    q4
    d 5,42
    s 1,10
    g 0


    1 4,21
    2 4,21
    3 3,8
    4 0
    5 2,09
    6 4,21
    7 4,21
    8 8,43

    ...and if i'm right with this,we could solder a small resistor from gain1 wire to gain pot lug1 cause when i turn pot all way down effect is muted.

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  15. This comment has been removed by the author.

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  17. Hel yea. I managed to fit this into a 1590B. My measurements weren't good enough to fit it in component side up, but it works! Go me.

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  18. Hey, just a little thing: according to the schematic there should be those little black thingy diode symbols in place of D3 and D4 on the layout(also in the description, they're missing). I'm looking forward to play with this!

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  19. Hi. I have a strange problem, I can't lower Q1's drain voltage under 8V even how hard I try to turn that trimmer (V is basicly same on both legs). With J201 on Q1 I can get drain voltage around 7v. I buy bunch of 2N5457's from ebay, are those faulty/fakes and reason for strange behavior? I also tried swapping to another trimmer and even 250k which changed nothing.

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  20. I bought some 2N5457 from local electric store and all good now. So got fakes from china. Oh no...how is that possible...:)

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  21. hi.
    according to the layout I assume D3 and D4 are red LEDs too, right?

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    Replies
    1. but according to the ROG's schematic it's 1N4148s

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